1. Field of the Invention
The present invention relates generally to methods for making polyarylene polyethers. More particularly, the present invention is directed to methods for making polyarylene polyethers where a bis-halobenzenoid compound or a dihaloaromatic compound and the double salt of a bis-hyroxybenzenoid compound or a dihydroxyaromatic compound are reacted in the presence of an aprotic polar solvent and an azeotrope former to produce a polyarylene polyether. Even more particularly, the present invention involves methods for making low molecular weight amine-terminated polyarylene polyethers.
2. Description of Related Art
Polyarylene polyethers are well-known and widely available thermoplastic resins. A conventional method for making polyarylene polyethers involves condensing substantially equimolar amounts of a bis-haloaromatic or dihaloaromatic compound (hereafter dihaloaromatic compound) and the double salt of a bisphenol or a dihydroxyaromatic compound (hereafter dihydroxyaromatic compound) in a reaction medium that includes an aprotic polar solvent and a compound capable of forming an azetrope with water. The azeotrope former is provided to help in removing water that is generated during the formation of the double salt of the dihydroxyaromatic compound. Exemplary methods for making high molecular weight polyarylene polyethers are described in U.S. Pat. No. 4,108,837.
Methods have been developed for making low molecular weight polyarylene polyethers that have a low degree of polymerization (Dp): For example, U.S. Pat. No. 4,275,186 describes a method for making hydroxy-terminated polyarylene polyethers having a low degree of polymerization. The method is similar to U.S. Pat. No. 4,108,837 except that a molar excess of the double salt of the dihydroxyaromatic compound is used.
Methods have also been developed for making low molecular weight polyarylene polyethers that are halogen-terminated. Typically, these procedures involve using an excess of dihaloaromatic compound in the reaction mixture. U.S. Pat. No. 3,539,655 and U.S. Pat. No. 3,563,951 describe procedures for making such halogen-terminated polyarylene polyethers. In addition, methods have been developed for making low molecular weight amine-terminated polyarylene polyethers by reacting an aminophenolate with a halogen-terminated polyarylene polyether or by reacting an aminophenolate with the reaction mixture used to make the halogen-terminated polyarylene polyether. Exemplary procedures are set forth in U.S. Pat. No. 3,895,064 and U.S. Pat. No. 3,920,768.
The methods for making polyarylene polyethers described in the above-identified patents were well suited for their intended purposes. However, numerous problems were encountered in trying to use these methods to reliably produce large amounts of polyarylene polyethers on an industrial scale and at a cost that was economically feasible.
In U.S. Pat. No. 4,789,722, a method was disclosed for making low Dp polyarylene polyethers wherein a dihydroxyaromatic compound and a strong and a relatively weak base are combined in a liquid reaction medium at 100° C.–200° C. to form a double salt that is then reacted with a slight molar excess of dihaloaromatic compound bearing two replaceable halogens. The method reliably produces halogen-terminated polyarylene polyethers of select degrees of polymerization and desirable correspondence between weight and number average molecular weights. In subsequent steps amine-terminated polyarylene polyethers are made using the strong and weak bases. The resulting amine-terminated polyethers have a low, select degree of polymerization, desirable correspondence between weight and number average molecular weight and a high level of amine termination.
The methods described in U.S. Pat. No. 4,789,722 have been routinely used to produce the large amounts of amine-terminated polyarylene polyethers that are required for industrial production. This has been accomplished in a relatively reliable and cost effective manner. However, as is the case with any complex large-scale industrial production process, there is always room for improvement. Accordingly, there is a continuing need to develop new methods for producing amine-terminated polyarylene polyethers that improve upon the reliability and/or efficiency of large-scale production of this commercially important thermoplastic material.